Pure compounds as extreme-pressure lubricants



Patented Mar. 8, 1938 UNITED. STATES PURE oomoimns A8 LUBRIO Elmer Wade m and George in. annuity. Hammond, Ind., assignon to Standard Oil Company, ana

GhicaIm-IIL, a corporation of Indi- No Application March 31, 1934;

\ Serial N0. 718,438

12 Claims.

This invention relates to an improved lubricant for use .on bearing surfaces which are subjected to high. pressures and high rubbing velocities during use. Y

5 v The present day trend in automotive design toward smaller rear axles and consequently smaller gears. On account of the small gears, tooth pressures and rubbing velocities are rapidly approaching a point where rear axles cannot 10 be lubricated satisfactorily with the ordinary mineral lubricating oils. The trend toward increasing loads on gear teeth in other fields has developed an urgent need for special lubricants. When hypoid gears, worm gears, heavy duty 15 bearings, planetary automatic shifts, and the like are used under conditions of high pressure and high rubbing velocities, special types of extreme-pressure lubricants must be provided in order to reduce the wear upon such moving parts.

2 Extreme-pressure lubricants are likewise important in cutting and drawing operations where the 011 must withstand high pressures encountered under those conditions of use.

The object of our invention is to .provide a lu- 5 bricant which will give satisfactory lubrication to bearing surfaces which are subjected to high pressures and/or high rubbing velocities. A further object is to provide a lubricant which will maintain a lubricant film on bearing surfaces at 30 all times. We have found that if small amounts of certain types of organic sulfur compounds are added to theJubn'cating oils and, soft greases, the lubricant will enable the bearing surfaces to withstand the high pressures and high rubbing velocities witho-utnoticeable wear. Similarly, these sulfur compounds may be incorporated into drawing lubricants and cutting oils.

We have found that the extreme-pressure lubricants can be prepared by adding a small quantity of an alkyl disulfide, high molecular weight alkyl sulfides, aryl thiocyanates and aryl isothioc'yanates, xanthic disulfides, or xanthates to mineral lubricating oils, preferably, those lubricating oils having aviscosity from about 90 to 200 seconds Saybolt at 210 F. These compounds may be used in oils designated as S. A. E. 20, 30, 40, 50, and 60 oils. These sulfur compounds are added in quantities ranging from V to 7%, but generally amounts ranging from 1 to 5% are satisfactory. The organic sulfur compounds may be dissolved in the oil .by any conventional mixing means. If desired, calcium and aluminum soaps or other soaps of high molecular weight fatty acids may be added to the composition to increase the viscosity or consistency (cl. a'z-o) of the lubricant. These extreme-pressure lubricants have substantially no corrosive action upon metal surfaces. v V The sulfur-bearing compounds which may be added to mineral lubricating ofls or greases to impart extreme-pressure lubricating properties thereto are as follows:

' R,ss1 2,

Buliideo wherein R and R1 represent alkyl groups containing at least 5 carbon atoms each gr aromatic groups such as phenyl radicals and tolyl radicals, however, when It represents a phenyl group, R1,

tolyl disulflde, and phenyl disulfide.

R SC E N Aryl thiocyanic esters R -N=C=S fAryl isothiocyanic esters wherein R4 represents aryl groups such,as

phenyl, tolyl and naphthyl groups. Examples of the aryl thiocyanic esters are phenyl thiocyanic ester, tolyl thiocyanic ester, and naphthyl thiocyanic ester. Examples of the aryl isothiocyanic esters or aryl isosulphocyanic esters are phenyl isos ulphocyanic ester, tolyl isosulphocyanic esters,

and naphthyl isosulphocyanicester. The aryl esters of isothiocyanic acid impart excellent extreme-pressure lubricating properties to mineral Wherein R5, R6, and R11 represent alkyl groups. Examples of the xanthic esters are ethyl xanthate ethyl'ester, methyl xanthate ethyl ester, ethyl xanthate methyl ester, ethyl xanthate butyl ester and ethyl xantha-te propyl ester. Examples 'of the xanthic disulfides are methyl xanthic disulfide and ethyl xanthic disulflde.

machine designed and operated on the same principle as the Almen extreme-pressure lubricant testing machine. 'lhose lubricants withstanding a bearing pressure of 20,000

pounds per sq. inch are satisfactory.

' Table I Sample: 5% of the following compounds dissolved in zero bright stock (mineral oil having a viscosity of 150 Saybolt at 210 F.)

'Speedofpin:150R.P.M.

Control Am lsulil 7 Met yl p-toluane sulicnatc.

Compounds y sulii Bntyl sulfide--. n-Hoptyl mercaptsnnn Eth benzene sulionate.

As stated hereinbefore, the sulfur compounds may be added to the viscous mineral oil by any suitable means. Generally the sulfur compounds are added to the mineral oil and stirred until a homogeneous mixture is obtained.

Example I Extreme-pressure lubricants for use under conditions of 'highrubbing velocities and pressures 1 or kerosene-range.

can be prepared satisfactorily by mixing 5% by weight of ethyl disulflde with a mineral oil having a viscosity of about 150 to -l Saybolt at 210 F.. Coastal mineral oils, Mid-Continent oils and paraflin mineral oils may be used'as the base for these extreme-pressure lubricants, Any of the hereinbefore mentioned compounds may. be used in the preparation of extreme-pressure lubricants instead of ethyl disulflde as set forth in Example I. v

The alkyl disulfldes may be prepared by any conventional means but if desired, they may be prepared from" the -mercaptans occurring in petroleum distillates boiling within the gasoline A petroleum distillate, preferably one containing a high percent of mercaptansis agitated with caustic. The caustic solution is separated from. the hydrocarbon material by decantation and then oxidized with any suit-' .able chemical reagent, for. example air, or ongen. The alkyl disulfldes are then removed from the oxidized caustic solution by boiling and are collected by absorption in a mineral oil solution; if

desired, they may be absorbed in the mineral oil captans in the petroleum distillate. Generally this temperature is below to'100" C. Other oxidinng agents such as hydrogen peroxide or potassium permanganate may be used instead of the oxygen. Also the high molecular weight alkyl disulfldes maybe prepared by treating hydrocarbon distillates with sodium plumbite solution and sulfur, separating the plumbite solution from the oil containing the dissolved disuliide and re covering the alkyl disulfldes by distilling the hydrocarbon oil fromthe dissolved disulfldes.

While we have described our invention with understood that our invention is not limited thereby, except as set forth in thefollowing We claim:

1. An extreme-pressure lubricant comprising, a mineral lubricating oil and from $5 to 5% of a disuliide having the following general formula: R+B8R1, wherein R and R1 represent substituents selected from the group consisting of alkyl groups or hydrocarbon phenyl groups. 2. An extreme-pressure lubricant comprising, a mineral lubricating oil and from ya to 5% of an alkyl disulflde having the following general formula: R-B-S-Ri, wherein R and R1 represent substituents selected from the class consisting of methyl, ethyl, propyl, butyl, amyl, hexyl, and cyclohexyl groups. g

3. An extreme-pressure lubricant comprising, a mineral lubricating oil having a viscosity from to 200 seconds Saybolt at 210 F. and from $5 to 5% of a butyl disulfide.

4. An extreme-pressure lubricant comprising, a mineral lubricating oil and from $5 to 7% of an organic sulfide having the following general formula: RPS-R1, wherein R and R1 represent alkyl groups containing at least 5- carbon atoms each.

5. An extreme-pressure lubricant comprising, a mineral lubricating oil having a viscosity from 90 to 200 sec. Saybolt at 210 F. and from 1 to 5% of an organic sulfide having the following general formula: RS--R1, wherein R and R1 represent substituents selected from the class consisting of V amyl. hexyl, and cyclohexyl groups. 7 6. An extreme-pressure lubricant comprising, a

mineral oil having a viscosity from 90. to 200 seconds Saybolt at 210 F. and from /2 to 5% of an organic disulfide selected from the group consisting of n-propyl disulfide, and n-butyl disulflde.

7. An improved liquid lubricant composition comprising a mineral lubricating oil and from $9 to 7% of a disulfide having the following general formula RS- SRi, wherein R and R1 represent substituents selected from the group consisting of alkyl groups and hydrocarbon phenyl groups.

'reference to particular examples, it should be i of an alkyl disulflde'having the following general I formula R--SS-R1, wherein R and R1 represent substituents selected from the group consisting of methyl, ethyl, propyl, butyl, amyl, hexyl and cyclohexyl groups.-

9. An improved lubricant composition comprising a mineral lubricating oil and from $6; to

7% ofan organic compound selected from the formula RS--R1, wherein R and R1 represent 7 group consisting of organic sulfides having thew phenyl groups or alkyl groups containing from 5 toB carbon atoms each; anddisulfides having the general formula Re-SSRa, wherein R: and

R: represent alkyl groups and hydrocarbon phenyl groups. p

10. An extreme-pressure lubricant comprising a mineral lubricating oil and from to'7% of an organic compound selected from the group consisting of organic sulfides having the formula R,-S-R1 wherein R and Ru represent alkyl groups containing from 5 to 6 carbon atoms each and di-sulfldes having the general formula Rz-S-S-R: wherein R: andR; represent alhi groups.

- 11. An improved lubricant composition comprising a mineral lubricating oil and from l to 7% of an organic compound, which has no cor- 'rosive action upon metal surfaces, selected from sent alkyl- 'groups.

the group consisting of organic, sulfides having the formula R'.S--R1 wherein R and R1 represent alkyl groups containing at least five carbon atoms each. and di-sulfldes having the general formula R '-s' s- Ra wherein R2 and R: repreprising mineral lubricating 5% of a 'disulflde having e following general formula R-S-S-R', wherein Band B represent alkyl groups.

GEORGE M. McNUL'l 'llf."

oil and from to 

